In a generic device for a coffee machine according to publication EP-A-2 120 656 B1, which corresponds to US 20100075007, it is possible to produce both cold and hot milk drinks as well as cold and hot milk foam for drinks containing milk foam such as cappuccino, latte macchiatto, white coffee or chocolate drinks.
As regards product quality, this type of coffee machine must always fulfil stringent requirements, even through its conditions of use and operation often vary. For example, for the quality of the milk froth that is produced the respectively prevailing atmospheric pressure plays an important role because, depending on the location of the coffee machine, be this on a mountain or at sea level, the amount of air that is supplied is affected by the different air pressures. Other factors are also the temperature and/or the nature of the type of milk that is used.
In the previously known coffee machines of the type specified at the start, the amount of air supplied can be set by hand by means of a throttle or similar means. However, during operation the amount of air which is set once is then exposed to the aforementioned disruptive factors that cause unintended fluctuations in the amount of air that is sucked in, and consequently the quality of the milk foam can change and be unsatisfactory.